A STUDY OF LIPOLYTIC ACTIVITY OF EPIDIDYMAL ADIPOSE TISSUE FROM VIEWPOINT OF RAT AGING / 体力科学

ABSTRACT

Lipolytic activity of adipose tissue with age has been widely investigated by many authors. There are differences on the conception of intrinsic lipolytic activity of a cell changed with aging. Since lipolytic activity has been expressed by amount of FFA release per wet weight, per triglyceride or per protein, increase of triglyceride or wet weight seems to be a main factor to affect on it. It is of interest, therefore, to investigate the intrinsic lipolytic activity of adipose tissue with aging from the relationship among FFA release, wet weight, protein and triglyceride content in adipose tissue.<BR>In the present paper, we investigated effect of aging on lipolysis by using epididymal adipose tissue in 29, 35, 43, 57, 105 and 350 days rats. Rats were anesthetized by intraperitoneal injection of pentobarbital sodium (4mg/100g body weight) and after that epididymal adipose tissue were removed and washed out the blood by 25°C Krebs-Ringer solution. The fat pads were placed in glass bottles containing Krebs-Ringer bicarbonate buffer solution (pH 7.2-7.4), bovine serum albumin (4°C/ w/v) and epinephrine (3.9 pM/ litre) . Incubations were carried out in a shaking water bath for 120 min at 37°C under an atmosphere of 95% O<SUB>2</SUB>-5% CO<SUB>2</SUB>. Rate of lipolysis were determined by assaying the production of free fatty acids. Free fatty acids were titrated by Dole's method. Triglyc-eride and protein content in fat pads were assayd by Stern and Shapiro's method and Lowry's method, respectively.<BR>The following results were obtained<BR>1) Triglyceride-to-wet weight ratio and triglyceride-to-protein ratio in the adipose tissue corresponded to age (days) remarkably increased between 35 days and 43 days rats. However, after that, triglyceride-to-wet weight ratio was unchanged up to 350 clays rats.<BR>2) Maximum lipolytic activity of adipose tissue in rats with aging was observed at 29 days in the range studied and after that its lipolytic activity decreased with aging. This decreased phase of lipolytic activity seemed to be divided into two phases one was fast decrease phase which was observed in the rats before 43 days, and the other was slow decrease in the rats after 57 days.<BR>3) Relationship between lipolytic activity and triglyceride-to-protein ratio in adipose tissue during aging showed inverse curvelinear relation, and it was found that lipolytic activity of adipose tissue was extremely inhibited at triglyceride-to-protein ratio more than ten.<BR>From these results, we assumed that increase of triglyceride content in adipose tissue was related with the decrease of lipolytic activity during aging and that the lipolytic activity of adipose tissue would be enhanced with decrease in triglyceride-to-protein ratio inversely.